The present invention relates to integrated circuit fabrication and, more particularly, to a method and apparatus for handling lithography mask containers.
Integrated circuits are manufactured from semiconductor wafers in semiconductor factories (xe2x80x9cwafer fabsxe2x80x9d). The wafers are processed in a variety of stations, among them lithography stations (xe2x80x9cexposure toolsxe2x80x9d). In the lithography station, the wafer is patterned by exposing it to electromagnetic radiation (e.g., ultra-violet light) going through a mask. The masks are sometimes referred to as lithographic reticle; an example is illustrated in U.S. Pat. No. 5,849,440. The masks optionally have pellicles to keep away particles.
Between lithography stations as well as between stations and storage facilities, the masks are carried in mask containers (also known as xe2x80x9creticle holdersxe2x80x9d). Usually, the containers are made from plastic.
Due to their extraordinary precision and complexity, the masks are very expensive. It is therefore of paramount importance to handle the mask and the containers with extreme care. The diligence of a human operator is relied on, for example, when masks and containers are identified with handwritten labels. Unfortunately, people are relatively slow, quickly fatigued by repetitive tasks, and handling errors are potentially catastrophic.
Mask identification such as, for example, a tracking number, a type classification of the mask, lithography tool classification, is provided on the mask itself for visual inspection. However, inspecting a mask requires the operator to remove the mask from the container. For reading identification in machine-readable form (e.g., barcode, OCR), it may also be required to put the mask into a lithography tool. Besides the time needed by the operator or by the tool for identifying, mask inspection might (i) cause the generation of particles, (ii) damage the mask, or (iii) mix up the order of multiple masks in a single container.
There is an ongoing need to provide an improved mask container which mitigates some or all of these disadvantages and limitations of the prior art.